In order to cross attending a casino on opening day off my list, I visited Lone Butte Casino, local casino in the greater Phoenix area, on opening day. Although I was able to park onsite, it felt like I parked a mile away. The casino was busy, every machine was being played, and it was difficult to get a sense of the games offered. If one isn't an invited guest, I'd recommend waiting until the next day to visit.
I give props to Horseshoe Cincinnati for arranging for offsite parking. I see this as no different than attending a baseball game at Chase Field. Some season ticket holders have parking passes that enable them to park in the garage that connects yo the stadium. Everyone else needs to park somewhere else.